1. Field of the Invention
The present invention relates to an information processing device and method.
2. Description of the Related Art
There is an increasing diversity in the formats of the video data that video reproduction devices are called on to reproduce. There are also devices, such as automotive navigation devices, that must be able not only to reproduce video data but also to rip audio data extracted from a compact disc (CD), and to display map data and video data from a camera. One way to provide these varied functions is to configure the processing control section of the device with a separate system on a chip (SoC) as a processing controller for each function. Devices with different combinations of functions can then be configured in a flexible manner by using as processing controllers a plurality of SoCs which have different functions respectively. Each SoC has a host unit for a bus that connects to an external media reader for reading data from external recording media.
In a device using this type of multiple-SoC processing control, the frequency of access to the external media reader varies from one SoC to another, depending on the function supported by the SoC.
For example, automotive navigation functions normally operate on an internal hard disk drive (HDD) or solid state drive (SSD), and need to access an external media reader such as an optical disc drive only infrequently, to update the data on its internal drive or to load additional data such as compressed audio data. In contrast, reproduction functions of a digital versatile disc (DVD) or Blu-ray disc (BD) frequently require connection to an optical disc drive.
A device that includes both an SoC for automotive navigation functions and an SoC for reproduction functions of optical discs can therefore read external media efficiently and economically by using a single optical disc drive for both purposes.
In Japanese Patent Application Publication No. 2005-235025, Hirose describes a configuration of this type, in which a single external media reader is shared by a plurality of host units by the use of a bus switch. When the host unit in one processing controller is connected to the bus through the bus switch, the host units in the other processing controllers are disconnected from the bus. A precondition for this configuration is that all host units must use the same bus specification, such as the conventional Advanced Technology Attachment (ATA) specification.
The serial ATA bus which is the next generation bus of the ATA bus has come into wide use. Compared with the conventional ATA bus, the serial ATA bus has the advantages of fewer signal lines and a higher data transfer rate. For these reasons, some automotive navigation devices incorporate an SoC having a host unit that supports only the serial ATA specification. When this type of SoC is combined with an SoC having a host unit that supports only the conventional ATA specification, the configuration taught by Hirose cannot be used.
A possible solution is to use a bridge to convert between ATA bus signals and serial ATA bus signals, as taught by Matsuda in Japanese Patent Application Publication No. 2009-032011. If the bridge taught by Matsuda is added to the configuration taught by Hirose, however, further problems arise.
A general problem is the increased cost of the circuit board and components used for video reproduction. A serial ATA bus transfers data at a rate of 1.5 gigabits per second. A circuit board with a data channel operating at this fast rate requires high-precision mounting techniques, and the bus switch which is included in the data channel must be a high-speed integrated circuit (IC). Advanced board design technology is also required. All of this is expensive.
Another problem with this scheme is that it can lead to unnecessary communication. If the bridge taught by Matsuda is inserted between a host unit and the bus switch taught by Hirose, for example, then the host unit remains electrically connected to the bridge even when the bridge is disconnected from the external media reader by the bus switch. In this situation, the serial ATA specification requires the host unit to transmit polling signals repeatedly to try to establish a connection with the external media reader. When the bridge is disconnected from the external media reader by the bus switch, such repeated polling serves only to waste processing resources and slows down the operation of the processing control section.